The biological and chemical aspects of the pheromones of several tick species will be investigated. The chemical aspects will be carried out in this laboratory, and the biological aspects will be done by the following collaborators, each with his own support: Dr. D.E. Sonenshine, Old Dominion University, Norfolk, Virginia, and Dr. Y. Rechav, Rhodes University, Grahamstown, South Africa. We have determined that 2,6-dicholorphenol is both necessary and sufficient to attract and sexually stimulate males of two species, Dermacentor andersoni and D. variabilis, and we have shown that the foveal gland is the release site. We propose further studies to delineate the biochemical pathways and to correlate pheromone production and release with feeding. The basic knowledge, though incomplete, has led to efforts to use the pheromone to disrupt tick mating on the host animal; these efforts will continue. Amblyomma hebraeum, a South African tick, mates following production by the male, of an assembly pheromone. Preliminary studies by Dr. Rechav incriminate both an orientation and an attachment component. We shall attempt to chemically identify the active compounds, and to extend these studies to the site and mode of pheromone production. Dr. Rechav will try to utilize the pheromone, which will be synthesized following identification, for control of this tick pest on cattle. Haemphysalis silacea, another South African tick will also be studied in the same way.